Method of making semiconductor device structures by means of ion implantation under a partial pressure of oxygen

Abstract

Disclosed is a simplified method of producing semiconductor device structures in an integrated technology using at least one ion implantation step. Implantation of the doping ions into a silicon wafer, for example, for producing a subcollector or an emitter, is not effected, as previously, in an ultra-high vacuum atmosphere through a thin protective layer of silicon dioxide which is applied by a separate thermal oxidation step prior to implantation, but the doping ions are directly implanted into the bare silicon wafer. The latter implantation is effected in an atmosphere of increased partial pressure of oxygen. Enhanced diffusion of the oxygen adsorbed at the surface occurs into the vacancies which are generated by the implanted doping ions close the surface of the silicon wafer. In this manner a silicon dioxide protective layer is formed already in the initial stage of ion implantation. As a result one process step can be saved, namely, the production of the protective layer by thermal oxidation prior to ion implantation.

What is claimed is: 
     
       1. A method of making semiconductor device structures using at least one ion implantation process for introducing dopants into a silicon semiconductor body comprising: (a) covering the silicon body with a suitable surface layer acting as a masking layer during the subsequent ion implantation process;   (b) forming in said masking layer according to the desired doping region pattern one or more openings where the bare silicon body surface is exposed;   (c) performing the implantation process of doping ions in an atmosphere having a significant partial pressure of oxygen thereby causing a protective silicon oxide layer to be formed on the exposed surface of said silicon body during the initial stage of said implantation process, for preventing channeling and subsequent contamination effects, and thus eliminating the need for a separate oxidation process prior to said ion implantation step, and   (d) subjecting the device structure to an anneal heat treatment to cause the diffusion and electrical activation of the implanted ions within the silicon body.   
     
     
       2. The method as defined in claim 1 wherein said protective silicon oxide layer is a silicon dioxide layer. 
     
     
       3. The method as defined in claim 2 wherein said ion implantation process is performed at a partial pressure of oxygen of p≧10 -4  pascal. 
     
     
       4. The method as defined in claim 3 wherein said doping ions are boron, phosphorus or arsenic ions. 
     
     
       5. The method as defined in claims 2 or 4 wherein said silicon dioxide protective layer is formed in the initial stage of the ion implantation process. 
     
     
       6. The method as defined in claim 5 wherein said silicon dioxide protective layer is formed with a thickness of 2 to 10 nanometer. 
     
     
       7. The method as defined in claims 4 or 6 wherein said desired doping region pattern includes the subcollector pattern, said ions are arsenic ions, and said implantation process is performed with a dosage of 2×10 16  ions/cm 2  at an energy of 40-75 KeV with said partial pressure of oxygen being about 5×10 -4  pascal. 
     
     
       8. The method as defined in claims 4 or 6 wherein said desired doping region pattern includes the emitter pattern, said ions are arsenic ions, and said implantation process is performed with a dosage of 10 16  ions/cm 2  at an energy of 40-75 KeV with said partial pressure of oxygen being about 5×10 -4  pascal. 
     
     
       9. The method as defined in claims 1 or 8 wherein the diffusion of the implanted doping ions into the silicon body is effected in an oxidizing atmosphere.